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[FAQ] LM5175: The difference between lm5175 and lm5176

SHENG YANG
Expert 1090 points
Part Number: LM5175
Other Parts Discussed in Thread: LM5176

Hi！Ti engineers！

What is the difference between lm5175 and lm5176?At present, the supply of lm5176 is difficult.Can lm5175 be used instead of lm5176?The current design specification is 8 ~ 36V input and 12V / 6A output.The specification lm5176 can meet the design requirements.I use WEBENCH ® Power designer, lm5175 can not meet this demand.Lm5175 can only realize 8 ~ 36V input and 12V / 3A output.Can lm5175 meet the requirements of 8 ~ 36V input and 12V / 6A output?Thank you for your reply.

  • 0
    TI__Guru 58225 points

    Hello Sheng,

    LM5176 is the predecessor of LM5175.

    LM5175 is in general able to support almost the same current as LM5176, it has a lower current capability in the buck-boost mode. Webench should support this, I will request an update.

    Please use the design calculator in the meantime: https://www.ti.com/tool/LM5175QUICKSTART-CALC

    Differences are in addition:
    - Needs different RT resistor
    - It is recommended to add 7.8V or 8.2V Zener diodes from SWx to BOOTx to stay below the abs max rating of 8.5V (layout dependent)

    Best regards,
    Brigitte 

  • 0 in reply to Brigitte
    Expert 1090 points

    Thank you very much.Brigitte !

    The second article on differences.As shown in the figure below.

    If the bias is used as the drive power input, the VCC may be greater than 8.5V. The threshold voltage will be exceeded.Ti's reference circuit output is 12V as bias, but the reference circuit does not add zener diode between SWX and bootX. Is it necessary to add diodes?

  • +1 in reply to SHENG YANG
    TI__Guru 58225 points

    Hello Sheng,

    Adding the diodes is a good design practice, as the undershoot on the switch node can overload the capacitor between BOOTx and SWx causing the device to get damaged.

    It is not necessary, but as these diodes are not integrated in the IC as in LM5176 it is highly recommended.

    Best regards,
    Brigitte

  • 0 in reply to Brigitte
    Expert 1090 points

    Thank you very much.Brigitte !